A React-based SVG renders a full-window smiley face whose yellow circular head, black stroke, and eyes are positioned relative to the window’s center coordinates. Using React 16.9 and ReactDOM, the component calculates dimensions from `window.innerWidth` and `window.innerHeight`, then draws the face with `<circle>` elements inside an SVG. The example demonstrates dynamic, viewport-adaptive sizing without a mouth, as only the head and two eye circles are included in the code.